Microphone transmitter



Patented l lg t.

Una ares? PATENT @Fldlltilgo HENRY G. REACH, OF BROOKLYN, NEW YORK,ASSIGNOR T ELECTEIEGAJL INDUSTRIES MANUFACTURING 00., OF NEW YORK,

N, Y., A CORPORATION @Ii' NEW? YORK.

MICROPHONE TRANSMITTER.

Application filed June 22, .1920. serial Ito. $90,898.

' To all whom it ma concern:

Be it known that I, HENRY G. LEACH, a citizen of the United States, anda resident of Brooklyn, in the county of Kings and State of New York,have invented certain new and useful Improvements in Microphonelransmitters, of which the following is a specification.

. The invention relates to telephone transmitters of the microphone typeemploying electrodes composed of a carbon or like diaphragm and a massof globular conducting material general] in the form of a pluralityofcarbon pe lets suitably retained. It has been found that transmitters ofthis type, while particularly sensitive to sounds of acertain pitch, donot respond so well to pitches ranging considerably. These transmitters,also, have a tendency to howl or whistle; and it is the object of thepresent invention to provide a microphone transmitter in which thistendency is greatly diminished, if not entirely obviated, and a diahragmwhich will respond and give a clarirange of pitch.

The nature of the invention will best be understood when described inconnection with the accompanying drawings, in whichi Fig. 1 is a planview with portions of the cover and diaphragms removed.

Fig. 2 is a partial vertical section thru the transmitter.

Fi 3 is a partial vertical section ofthe supp ementaryg diaphragm andretainer therefor. I

Similar characters of reference designate corresponding parts thruoutthe several to views.

Referring to the drawings, 10 designates a suitablecasing provided witha removable screw cap or cover, 11 having centrally disposed openings 12therein thru which aerial sound waves may freely enter. Within thecasing is designed to be included the microphonic transmitting elementscomprising two electrodes, for example a carbon dia phragm 13 whosecentral portion rests over ed tone to sounds comprised in the normal andmakes contact with a plurality of globular carbon pellets 14 arranged ina suitable supporting member 15 having circularly disposed conicalcavities 16, for example. As is well understood, vibrations imparted tothe diaphragm 13 will serve to vary the electrical resistance betweenthe two electrodes and thereby the current flowing in an externalcircuit (not shown).

As heretofore noted, however this type of transmitter possess certaininherent disadvantages, due principally to the fact that the aerialsound waves impinge directly on the diaphragm 135 and, in accordancewith the present inventlon, a supplementary diaphragm is provided toprevent this action, the sound waves bein received directly by saidsupplementary iaphragm. For example, a diaphragm 20 composed preferablyof silk or other meshed material or a membrane, and which has been preared or impregnated with a suitable me ium serving to stretch the sametaut and substantially fill the interstices thereof, may be mounted inpredetermined spaced relationship over the spacing and both diaphragmsbeing hel by the cap 11 to the casing 10.

There is thus provided an air cushion between the two diaphragms; andfurthermore, the sound waves are excluded from-direct action on the diahrs. 13 which is afiected solely by the vibrations of the diaphragm 20transmitted thereto thru the said air cushion. No violent concussionsare thereby permitted to act upon the resistance varying members and aclarified tone is obtained and whistling and howling eects greatlydiminished.

Various media may be employed for the supplementary diaphragm 20, but Ihave found Japanese silk impregnated with collodion to be very efiectivefor this purpose; and also a distance of fifteen one-thoutilt tilt

sandths of an inch between diaphragms to intermediate air cushion andconsisting of afi'ord a suitable air cushion. Japanese silk impregnatedwith collodion I claim: v stretching the same. 10 In a telephonetransmitter of the charac- Signed at New York in the county of New 5 terset forth and including a resistance vary- York and State of'New Yorkthis 21st day ing diaphragm; a supplementary diaof June A. D. 1920.phragm separated therefrom to provide an HENRY G. LEACH.

